Research Journal of Environmental and Earth Sciences 3(3): 261-268, 2011
ISSN: 2041-0492
© Maxwell Scientific Organization, 2011
Received: December 17, 2010 Accepted: January 16, 2011 Published: April 05, 2011
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Abstract: The naturally occurring radioactive materials associate with building materials from twelve (12) towns along coastal part of Central Region of Ghana have been studied. The activity concentration of 238 U, 232 Th and 40 K ranged from 27.90±1.06 to 97.89±6.34 Bq/kg, 15.47±0.97 to 70.97±5.83 Bq/kg and 89.34±5.20 to
943.44±34 Bq/kg, respectively. The 238 U recorded the highest value of 97.89±6.34 Bq/kg in granite from
Ampenyi whilst pebbles from Winneba recorded the lowest activity concentration. The 232 Th activity concentration level ranged from 15.47±0.97 to 70.97±5.83 Bq/kg with clay soil from Kormantse recording the highest whiles pebbles from Apam had the lowest average activity concentration. The average activity concentration of 40 K ranged from 89.34±5.20 to 943.44±34 Bq/kg , with the highest activity concentration level occurring in Ampenyi and lowest level of the activity concentration also occurring in beach sand from Apam.
The activities are compared with available data from other publications and with the world average value for soils. The radium equivalent activity Ra eq
, the external hazard index (H ex
) (0.17 to 0.48), Internal hazard index
(H in
) (0.25 to 0.72), the absorbed dose rate D in air (36.90 to 131.29 nGy/h) and the annual effective dose ( E
T
)
(181.02 to 644.00
:
Sv/yr) were evaluated to assess the radiation hazard for people living in dwellings made of these building materials. The studies indicated that the main contributions to gamma–radiation in building materials are 40 K, 238 U and 232 Th. The results obtained were found to be within the allowable limit of 1mSv per year for public exposure control recommended by the International Commission Radiological Protection (ICRP) and Organization for Economic Cooperation and Development (OECD).
Key words: Building materials, effective dose, external and Internal hazard indexes, NORMS , gamma spectrometry, radium equivalent
INTRODUCTION
Naturally occurring radioactive materials (NORMS) are acknowledged as the largest sources of exposure to human health (UNSCEAR, 1993, 2000). It is also established that ionizing radiation may cause damage to human tissues and other biological systems (Arafa, 2004;
Darko et al ., 2005). The building materials and their processed products contain radionuclides of the two most commonly known radioactive series namely, the uranium and thorium series as well as potassium-40 (Amrani and
Tahtat, 2001; Ngachin et al ., 2007; Swedjemark, 1977).
In recent times, attention has been paid to artificial radionuclides than radionuclides of natural origin, though it is known that the contribution of artificial radionuclides in our environment is much smaller (UNSCEAR, 2000).
Natural radionuclides in building materials namely soil, sandcrete block, concrete block and granite generate significant component of background radiation exposure of the global population.
Radiation exposure due to the building materials can be divided into external and internal exposures. The external exposure is caused by direct gamma radiation whereas the internal exposure is caused by the inhalation of radioactive inert gas radon ( 222 Rn, a daughter product of 238 U) and its short-lived secondary decay products. In order to assess the radiological hazards to human health, it is important to study the radioactivity levels emitted by the building materials (Leung et al ., 1998).
The radiations which humans are exposed to may increase if they live in houses or buildings constructed using materials whose radiation doses are above normal background radiation level in the area (Cliff et al ., 1985).
The radiological implications of living or working in buildings made from these building materials is the increase in external exposure of the body due to
Corresponding Author: F. Otoo, Radiation Protection Institute, GAEC, Box LG 80, Legon, Ghana. Tel: +233 243 102 487;
Fax: +233 302 400 807
261

gamma - emitting radionuclides (Beretka et al ., 1985;
Dainius and Aloyzas, 2007).
A number of studies on radioactivity in building materials have been carried out in many different countries around the world for the purpose of estimating the population exposure to natural background radiation. (Al-Jarallah et al ., 2001; Arafa, 2004;
El-Dine et al ., 2001; Giuseppe et al ., 1996;
Hussain et al ., 2010; Kovler et al ., 2002;
Malanca et al ., 1993; Muhammad et al ., 2001;
Ngachin et al ., 2007; Petropoulos et al ., 2002;
Sroor et al ., 2001; Stoulos et al ., 2003;
Tzortzis et al ., 2003; UNSCEAR, 1988). In Ghana there are a few comparable studies in building materials
(Andam, 1994). Most studies carried out have concentrated on radioactivity in soils and rocks
(Andam, 1994; Darko et al ., 2005; Yeboah et al ., 2001).
Knowledge of the activity of naturally occurring radioactive materials (NORMS) is very important due to the fact that it constitutes the largest source of population exposure, and its assessment will lead to setting up of radiation protection exposure level.
Results from the study will provide useful data and information on radioactivity levels in building materials and aid in decision-making processes in setting up guidelines for the control of radiation exposure in dwellings in Ghana. It will also engender interest for further research into NORMS in all types of building materials from all the geographical regions of the country.
EXPERIMENTAL METHOD
Sample collection and preparation: The samples were collected from coastal areas of Central Region of Ghana between the periods of January to June and brought to the
Environmental Laboratory of Radiation Protection
Institute, Ghana Atomic Energy Commission to conduct the experimental work.
The building materials collected from the coastal communities and towns for this study include granite, clay soil, sandcrete, sandy soil, beach sand, and pebbles.
Samples with large grain size were crushed, ground, homogenized, air-dried and sieved to a umiform mixture to particle size of about 5
: m, sealed in 1.0 L Marinelli beaker and stored at room temperature for period of 3-4 weeks to allow 238 U and 232 Th decay series to reach radioactive equilibrium with it short live progeny (Amrani and Tahtat, 2001; Khan et al ., 1992, 2002;
Kumar et al ., 2003).
Gamma spectrometric measurements:
Gamma spectrometry: The gamma spectrometer used for this work consists of a detector, preamplifier and detector bias supply, pulse-height analyzer, data readout capability, and shielded sample enclosure. The detector is made up of a high purity germanium (HPGe) detector
Res. J. Environ. Earth Sci., 3(3): 261-268, 2011 coupled to a multichannel analyser (MCA) with software for data acquisition. The logic control capabilities allow data storage in various modes and display or recall of data.
The detector crystal has a diameter of about 36 mm and thickness of about 10 mm. The crystal is housed in an aluminium canister with a 0.5 mm thick beryllium entrance window. A lead shield, built with 5 cm thick lead bricks surrounds the detector to prevent it from external radiation reaching the detector. The detector is coupled to a Canberra 1510 signal processing unit which contains the power supply, amplifier and analog to digital converter.
Digitized counts are collected in a Canberra S100 multichannel analyzer. Spectrum acquisition and analysis are performed with APTEC software. The Germanium detector is connected to an Uninterrupted Power Supply
(UPS). The ambient temperature around the detector was relatively fluctuated between 16 and 27ºC during the period of measurement and detector was then cooled down to about 77 K by liquid N
2
.
Calibration of the gamma spectrometry and activity concentration: The detector and measuring assembly was calibrated for energy and efficiency in order to determine the type of radionuclides and the quantities present. The calibrations were done manually using a 1.0 L Marinelli beaker with mixed radionuclide standard solution supplied by the IAEA. The standard solution contains the following radionuclides with corresponding energies
241 Am (60 keV), 109 Cd (88 keV), 57 Co (122 keV), 139 Ce
(1656 keV), 203 Hg (279 keV), 113 Sn (391.69 keV), 85 Sr (514 keV), 137 Cs (662 keV), 88 Yt (898 keV and 1836 keV) and
60 Co (1173 keV and 1333 keV).
The samples were counted for 36,000 s. Background measurements were also made for the same period and subtracted from the samples (Darko et al ., 2005;
Yeboah et al ., 2001) with the high resolution gamma ray spectrometer made up of high purity germanium (HPGE) detector and counting assembly. The Canberra S100
MCA and APTEC software programme were used for spectrum acquisition and analysis. The weight of each sample, sampling date and time, counting date and time were recorded.
The activity concentration (Bq/kg) in each of the sample in the spectrum was calculated using the analytical expression (Beck et al ., 1972):
A
C
= where, M sam
N sam
P E
E T
C
* M sam
(kg) is the mass of sample, N sam
is the counting time in seconds,
0
(E) is the photopeak efficiency.
(cps) is the net peak area for the sample in peak range, P(E) is the gamma emission probability, T
C
(1)
262

Res. J. Environ. Earth Sci., 3(3): 261-268, 2011
The activity concentrations of the parent nuclides were obtained using their daughter nuclide activity concentrations assumption of attainment of secular equilibrium within the period of storage. The transition lines (609.34, 1764.51 keV) of 214 Bi and (583.32, 2614.56
keV) of 208 TI were used to determine the activity concentration of 238 U and 232 Th, respectively. 40 K was determined directly with its only 1460.75 keV peak transition line. whiles clay soil from Kormantse measured activity concentration twice greater than worldwide average activity concentration of soil (25 Bq/kg). The most significant radionuclide identified was content in all the building materials was higher than those of other radionuclide. The results also indicate that the main contributions to gamma-radiation in the building materials are 238 U, 232 Th and 40
40 K. The 40 K
K. Due to the different composition of building materials and uneven distribution of the radionuclides in the samples, the quantities of natural radionuclides are also found to be different
(Kathren, 1998). The variation in the figures observed in the different location is a function of the local geology and could be attributed to the physical and chemical sorting of the materials from location to location.
RESULTS AND DISCUSSION
Activity concentration: In this study forty-six (46) samples from twelve (12) different towns along coastal part of central region of Ghana were investigated. The building materials were measured for natural radionuclides such as 238 U, 232 Th and 40 K. The activities concentrations were calculated according to UNSCEAR
(2000) report. The Table 1 shows activity concentration of each radionuclide in the measured sample together with their corresponding uncertainties. The average activity concentration of 40 K ranged from 89.34±5.20 Bq/kg in the beach sand from Apam to 943.44±34 Bq/kg of granite from Ampenyi. The average activity concentration of 238 U vary from 27.90±1.06 to 97.89±6.34 Bq/kg with granite from Ampenyi measured the highest activity while pebbles from Winneba recorded the lowest activity concentration. The average activities concentration of
232 Th range from 15.47±0.97 to 70.97±5.83 Bq/kg with clay soil from Kormantse recorded the highest while pebbles of Apam had the lowest average activity concentration. The granite samples from all the locations in the central region and clay soil from Kasoa and
Komenda recorded a value exceeding the worldwide average activity concentration with other building materials shown relative radioactivity level lower than world average value of 370 Bq/kg (Bou-Rabee and
Bem, 1996). The average activity concentration of 40 K from granite in Kasoa, Saltpond, Biriwa, Ampenyi and
Komenda measured activity concentration greater than twice of the average worldwide soil activity concentration. The 238 U content in all building materials investigated measured activity concentration greater than that of average worldwide of (25 Bq/kg). The average activity concentration of granite from Kasoa, Apam,
Saltpond, Kormantse, Ampenyi and clay from Kasoa were more than 3 times the worldwide average activities concentration of 238 U of soil with exception of Komenda which recorded average activities far greater than 4times the worldwide average activity concentration.
The average activity concentrations of 232 Th in building materials investigated were more than the worldwide average activity concentration with exception of pebbles from Apam and beach sand from Komenda,
Calculation of radiation hazards:
Radium equivalent activity: The 226
Ra eq
= A
C
(Ra )+1.43* A
C
(Th) +0.077* A
C
(K) (2) where, A
Bq/kg of
C
226
( Ra )
,
Ra,
A
C
232
( Th ) and A
C
( K ) are average activity in
Th and 40 K, respectively.
Equation (2) is based on the fact that 370 Bq/kg of
226 Ra, 259 Bq/kg of 232 Th and 4810 Bq/kg of 40 K produce the same gamma dose equivalent (Stranden, 1976; Krisiuk et al ., 1971; UNSCEAR, 1988) which implies that a radium equivalent of 370 Bq/ kg in building materials will produce an external exposure of about 1.5 mSv/y to the population (Beretka and Mathew, 1985; OECD, 1979).
Though Ra eq
equivalent values calculated as shown in
Table 2, varies from the same building materials from different locations collected. However, it is clear from this table that the Ra eq
values obtained is less than 370 Bq/kg which is the recommended limit by OECD.
External hazards index:
1985; Hayambu et al ., 1995):
Ra, 232 Th and 40 K are not uniformly distributed in building materials. In order to determine the specific activity of each building materials, the radium equivalent activity calculated using the expression (Beretka and Mathew, 1985; Hayambu et al ., 1995; Tufai et al ., 1992):
To restrict the external gamma radiation dose from building materials to 1.5 mSv/ year or unity. The model below is used as dose criterion to calculate external hazard index (Beretka and Mathew,
H ex
= A
C
(Ra)/370+ A
C
(Th)/259+A
C
(K)/4810 where A
C
(Ra), A concentration of 238 U,
C
232
(Th) and A
C
Th and 40
(K) are the activity
K expressed in Bq/kg.
External hazards index value should be less than unity for probability of risk to be negligible
(Hayambu et al ., 1995). The calculated values of external
263

Res. J. Environ. Earth Sci., 3(3): 261-268, 2011
Table 1: Activity Concentration of 238 U, 232 Th, and 40 K in the building materials investigated
Activity concentration(Bq/kg)
Sample location
Kasoa
Sample type
Granite
Clay soil
----------------------------------------------------------------------------------------------------------
40
K
238
U
232
Th
818.51±31.92
397.06±21.82
88.51±7.04
77.54±4.98
56.38±3.56
49.44±4.47
Winneba
Apam
Otuam
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay soil
Sandy soil
165.22±6.91
59.61±4.00
137.04±5.56 45.41±2.30
101.02±3.82
372.94±16.56
785.35±27.07
342.47±21.31
106.38±5.27
82.92±5.20
94.36±9.25
283.63±16.13
695.96±36.06
364.65±21.07
107.63±9.13
89.34±5.20
95.38±4.31
197.19±15.39
677.53±25.13
362.05±4.31
99.05±4.31
43.61±2.28
33.90±3.01
66.22±4.51
36.36±2.55
51.82±3.43
45.55±3.31
52.46±3.50
27.90±1.06
75.76±5.70
83.59±3.60
53.55±3.31
48.78±2.93
50.13±4.01
49.15±2.80
67.61±4.00
58.25±3.60
50.31±3.02
30.75±3.07
33.55±2.39
37.09±2.39
27.07±2.12
44.80±3.04
29.08±1.98
27.38±2.45
29.71±2.16
34.05±2.50
23.07±1.12
54.25±3.33
35.38±2.83
28.21±2.04
39.71±2.23
38.23±2.44
15.47±0.97
55.65±3.09
46.50±3.02
38.37±2.54
Edumafa
Saltpond
Kormantse
Abandze
Biriwa
Cape coast
Ampenyi
Beach sand
Sandcrete block
Pebbles
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
86.89±4.51
94.38±9.27
194.22±14.51
599.23±26.30
327.63±10.13
97.63±10.13
76.28±5.37
81.74±5.03
282.68±15.07
795.80±31.67
344.31±19.55
126.73±9.55
109.05±5.31
116.89±4.66
128.89±5.81
549.75±27.45
264.65±14.02
142.47±13.41
115.25±11.07
99.45±10.36
105.62±5.81
716.36±26.70
305.20±18.69
105.05±5.32
107.99±5.33
95.63±10.13
289.63±10.10
777.38±29.74
256.11±12.68
102.02±9.82
152.47±14.31
98.55±10.29
289.28±8.37
689.36±26.70
299.10±14.78
143.73±11.30
115.24±5.71
97.92±9.66
187.79±4.71
943.44±34.57
259.96±14.67
116.75±11.56
109.98±5.34
92.02±9.82
297.51±9.39
45.55±3.31
51.31±3.02
36.26±2.55
62.86±3.30
64.69±4.79
48.90±3.06
49.23±3.07
45.82±3.02
43.55±2.31
95.19±3.25
83.07±7.43
42.55±3.31
49.31±3.02
57.55±4.60
52.20±3.97
76.56±4.07
69.48±4.96
54.31±4.90
58.61±4.03
44.82±4.12
41.59±4.32
69.24±4.52
67.61±4.00
62.96±3.90
57.24±4.40
55.42±4.83
50.36±4.05
74.68±5.08
71.65±5.06
53.82±4.27
52.82±4.27
50.33±4.02
62.33±4.07
67.72±4.54
59.63±4.89
60.71±4.40
61.45±4.92
57.88±3.95
53.84±4.28
97.89±6.34
75.69±5.05
58.55±4.60
48.05±4.45
63.87±3.94
53.84±4.29
39.47±3.94
26.16±3.25
44.69±4.92
49.85±3.97
37.71±3.79
33.92±3.25
28.55±3.47
74.57±5.04
46.97±4.48
55.52±4.34
49.41±4.57
37.26±3.53
28.59±3.49
36.21±24.44
35.90±2.28
29.10±1.98
34.25±2.50
58.38±4.33
33.07±2.12
38.17±2.54
31.31±2.04
38.21±2.06
42.42±1.30
57.39±3.55
40.21±3.01
37.37±2.54
51.50±4.32
43.43±1.30
50.44±4.49
70.97±5.83
38.48±3.81
39.75±3.60
46.80±4.03
41.38±3.56
46.16±3.94
38.75±3.59
34.35±3.50
35.25±3.50
41.99±4.34
39.29±3.57
48.97±4.45
47.94±4.47
27.58±3.48
37.58±3.48
38.27±3.54
264

Res. J. Environ. Earth Sci., 3(3): 261-268, 2011
Table 1: Continued
Komenda Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
778.51±31.37
385.37±16.69
188.27±14.05
98.75±10.39
99.73±10.55
284.89±14.65
105.07±9.31
58.53±4.07
59.61±4.03
49.17±4.12
59.56±4.63
58.88±3.95
46.12±3.72
44.38±3.57
39.75±3.94
17.51±2.99
53.50±4.33
29.93±3.28
Table 2: Calculated radium equivalent, internal and external hazards, absorbed dose rates and effective doses due to natural radionuclides in the building materials investigated
Sample location
Kasoa
Winneba
Apam
Otuam
Typeof sample
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
102.18
112.45
112.14
86.46
199.36
152.62
112.81
104.02
109.91
Ra eq
(Bq/kg)
232.16
174.44
143.03
99.94
99.37
115.66
190.76
104.32
99.17
94.42
108.42
82.73
206.93
162.26
0.55
0.32
0.39
0.36
0.42
0.25
0.64
0.60
H in
0.72
0.61
0.52
0.37
0.38
0.34
0.40
0.42
0.42
0.33
0.60
0.50
0.42
0.39
0.42
0.37
0.22
0.25
0.24
0.28
0.17
0.43
0.37
H ex
0.48
0.40
0.36
0.25
0.25
0.24
0.26
0.29
0.30
0.20
0.41
0.35
0.29
0.27
0.28
Absorbed dose
Rate (nGy/h)
109.90
87.49
65.44
45.72
45.30
54.91
91.23
49.35
44.93
42.81
49.15
39.25
97.86
74.74
46.28
51.13
50.97
39.67
94.52
71.16
51.30
47.31
49.89
Effective dose
(
:
Sv/y)
539.09
429.17
321.00
224.26
222.19
269.35
447.52
242.08
220.42
210.00
241.08
192.52
480.05
366.62
227.03
250.79
250.04
194.60
463.68
349.09
251.63
232.06
244.71
Elimina
Saltpond
Kormantse
Abandze
Biriwa
Pebbles
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay soil
Sandy soil
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
92.83
157.98
173.40
103.71
109.68
96.89
119.96
217.13
191.66
109.81
111.15
140.20
124.23
191.02
191.35
120.31
124.33
119.49
108.90
195.11
142.74
119.94
119.39
123.05
128.82
204.57
159.93
101.12
118.30
112.64
141.05
0.31
0.49
0.58
0.40
0.42
0.37
0.37
0.70
0.68
0.39
0.41
0.51
0.45
0.62
0.66
0.45
0.47
0.43
0.39
0.57
0.52
0.48
0.45
0.47
0.43
0.61
0.58
0.40
0.44
0.42
0.50
0.22
0.31
0.41
0.26
0.28
0.25
0.27
0.44
0.46
0.27
0.28
0.36
0.31
0.42
0.47
0.30
0.32
0.31
0.28
0.38
0.34
0.31
0.30
0.32
0.30
0.41
0.39
0.255
0.29
0.29
0.33
43.09
74.95
80.39
47.10
49.74
43.94
56.00
102.51
88.32
50.36
50.62
63.90
56.73
89.53
88.19
54.91
56.46
54.61
49.84
93.10
65.57
54.17
54.44
55.88
59.92
97.30
73.42
45.74
54.09
51.22
65.18
211.39
367.64
394.36
231.06
244.02
215.55
274.72
502.86
433.24
247.02
248.32
313.44
278.29
439.16
432.60
269.36
276.95
267.90
244.47
456.68
321.64
265.73
267.03
274.11
293.94
477.30
360.17
224.38
265.34
251.25
319.72
265

Res. J. Environ. Earth Sci., 3(3): 261-268, 2011
Table 2: Continued
Cape Coast
Ampenyi
Komenda
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block
Pebbles
Granite
Clay
Sandy
Beach sand
Sandcrete block pebbles
158.21
146.57
143.06
124.25
113.93
109.13
277.17
162.87
146.93
127.18
124.24
117.63
230.97
151.67
130.95
81.81
143.74
123.62
hazards index for these building materials ranged from
0.17 to 0.48 with the lowest dose occurring in pebbles from Winneba while highest external dose in granite sample obtained from Kasoa.
0.48
0.50
0.53
0.48
0.45
0.41
0.84
0.60
0.54
0.45
0.49
0.41
0.76
0.50
0.48
0.34
0.53
0.44
Internal hazards index: There is also radiation hazard threat to respiratory organs due to the 222 Rn, decay product of 226 Ra, and its short-lived decay product. To determine this threat the worldwide maximum radium activity content must be reduced to half of the normal limit. Therefore the model used to calculate this hazard is shown below (Beretka and Mathew, 1985;
Hayambu
H in et al
= A
C
., 1995):
(Ra)/370+ A
C
(Th)/259+A
C
(K)/4810 where,A
C
(Ra), A
C concentration of 238
(Th) and A
U, 232 Th and
C
40
(K) are the activity
K expressed in Bq/kg.
Table 2 indicates the values of hazard index ranging from the 0.25 to 0.72, with highest value occurring in granite from Kasoa and the minimum internal hazards index found to be 0.25 in the pebbles from Winneba.
Absorbed dose rate and effective dose rate: absorbed dose rate D(nGy/h) was calculated for the building materials using the formula proposed by
(UNSCEAR, 1993):
D = 0.429*A
C
(U)+0.666*A
C
(Th)+0.042*A
C
The
(K) where,0.429, 0.666 and 0.042 are Dose constants for 238 U,
232 Th and 40 K,respectively.
A
C
(U), A
C
(Th) and A
C
(K) are the mean activity concentration of 238 U, 232 Th and 40 K expressed in Bq/kg.
The absorbed dose in air commuted ranged from
36.90 to 109.90 nGy/h. Most of the values obtained are greater than worldwide average value of soil (55 nGy/h)
0.30
0.34
0.36
0.32
0.29
0.26
0.57
0.39
0.38
0.32
0.32
0.26
0.48
0.34
0.32
0.20
0.37
0.28
75.43
67.91
65.28
56.32
51.53
50.00
131.28
74.67
67.00
58.14
56.08
54.63
108.49
70.85
59.95
36.90
65.37
57.16
370.00
333.11
320.23
276.26
252.79
245.26
644.00
366.29
328.65
285.20
275.10
268.00
532.18
347.56
295.00
181.02
320.67
280.38
(Yang et al ., 2005) and also UNSCEAR reported average value ranged from 18 to 93nGy/h (UNSCEAR, 1993,
2000). The values obtained by this investigated building materials are greater than the worldwide average of soil report by (Yang et al ., 2005) and lie within the worldwide values report by (UNSCEAR,1993, 2000) with exception of granite from Kasoa, Biriwa, Abandze, Saltpond,
Otuam, Komenda and Ampenyi.
Annual effective doses: The annual effective dose rate E
T
(mSv/yr) from radionuclide in the building material were also calculated on the basis of the mean activity concentrations and absorbed dose rate in air. The
Equation below was used to calculated Annual effective dose rate, E (mSv/yr):
E
T
= ( 238 U, 232 Th, 40 K) = D*0.7(Sv/Gy)*24*365*0.8 h/y where,D is absorbed dose rate in air (nGy/h) and 0.7 is the dose conversion factor from gray to sievert
(UNSCEAR, 1988), 0.8 is the indoor occupancy factor.
The annual effective dose rate varies from 181.02 to
644.00
:
Sv/yr. The highest annual effective dose rate occurring in granite from Ampenyi whiles the lowest annual effective dose resulting in the beach sand from
Komenda. The granite from the following locations Kasoa
(539.090
:
Sv/yr), Apam (480.05
:
Sv/yr), Otuam (463.68
:
Sv/yr), Saltpond (502.86
:
Sv/yr), Biriwa (477.31
:
Sv/yr) and Ampenyi (644.00
:
Sv/yr) recorded the annual effective doses which are greater than the world average effective dose of 460.00
:
Sv/yr for soil
(Yang et al ., 2005).
CONCLUSION
NORMS and its related radiation hazards in building materials along coastal part of central region of Ghana have been studied using gamma spectrometry.
266

Res. J. Environ. Earth Sci., 3(3): 261-268, 2011
The activity concentration levels of various radionuclides were also determined. The 238 U content ranged from 27.90±1.06 to 97.89±6.34 Bq/kg with granite from Ampenyi measured the highest activity while pebbles bricks from Winneba recorded the lowest activity concentration.
The 232 Th activity concentration level range from 15.47±0.97 to 70.97±5.83 Bq/kg with clay soil from
Kormantse recorded the highest whiles pebbles of Apam had the lowest average activity concentration. The average activity concentration of 40 K ranged from
89.34±5.20 to 943.44±34 Bq/kg, with the highest activity concentration level occurring at Ampenyi and lowest level of the activity concentration also occurring in beach sand from Apam. The radium equivalent (Ra eq
) varied from
81.81 to 232.16 Bq/kg. The highest value occurring in granite sample from Kasoa whiles the lowest value occurring in beach sand from Komenda. The absorbed dose rate in air ranged from 36.90 to 131.29 nGy/h with the maximum dose rate resulting in granite from Ampenyi whiles minimum dose rate in air occurring in beach sand from Komenda. The annual effective dose rate varies from 181.02 to 644.00
:
Sv/yr. The highest annual effective dose rate occurring in granite from Ampenyi whiles the lowest annual effective dose resulting in the beach sand from Komenda.
The activity concentration of 238 U, 232 Th and 40 K investigated are found to be normal and within the average worldwide ranges. The Radium equivalent, external and internal indexes, absorbed dose rate in air and annual effective doses calculated are within the values found in other countries. The values were also found to be within the limit for public exposure control set by the ICRP 60 and OECD (ICRP 60, 1991;
OECD, 1979). Thus, no significant radiological hazards arise from using building materials along coastal part of central region of Ghana for construction of houses.
The results may not reflect the real situation in all types of building materials in the selected studied areas.
For more accurate results that better may represent the regions of the country, detailed studies can be carried out for all the different types of building materials used, using higher number of samples. This study can also be used as a reference for more extensive studies and the results serve as a source of information to assist in the formulation of regulatory guidelines for decision-making in Ghana.
ACKNOWLEDGEMENT
The authors are grateful to the Radiation Protection
Institute of the Ghana Atomic Energy Commission for the use of their facilities for this study. The Building and
Road Research Institute (BRRI) of the Council for
Scientific and Industrial Research, Kumasi Ghana are also commended.
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